The raw sewage discharged from humans is typically discharged into a sewage system by a flush toilet or the like and then flows into a river after purification in a holding tank. However, at events such as festivals, athletic events, fairs, meetings and the like, temporary toilet facilities must be provided for disposal of raw human waste.
Employed conventionally are movable temporary toilets, most of which have a tank for temporarily storing the raw sewage therein. However, temporary toilets require the raw sewage contained in the tank be sucked into a vacuum truck, and the collected raw sewage must then be transferred to a sewage purifying facility. This is laborious and time consuming and is unhygienic.
Transportation vehicles such as trains and buses, which operate over long distance, are provided with a tank exclusively for storing the discharged raw sewage. The raw sewage in this tank is subjected to a chemical deodorizing treatment and is thereafter collected by a vacuum truck at a terminal or collection point.
The storing, collecting and disposal methods are thus not modern and are very unhygienic. If the temporary toilet has been used for a long period of time, the raw sewage in the tank causes a bad smell, and operators dislike disposing of the raw sewage.
In an attempt to ameliorate the above problems, there have been proposed several hygienic disposal methods. In one method, chemicals are introduced into the raw sewage storage tank to prevent the generation of the bad smell and to effect sterilization of the sewage. This method, however, cannot be used for a long period of time because the chemicals become diluted, and costs are high, though this method is often employed in transportation vehicles.
In another method, the raw sewage is contained in a bag made of vinyl or the like to prevent the diffusion of the bad smell. This method, however, requires a vinyl bag of large size and involves a high cost for disposal thereof, and it is troublesome to separate the raw sewage from the bag. A large-scale disposal facility is also required.
In still another method, the discharged raw sewage is directly dried by use of heat from a burner, etc. Since the primary component of raw sewage is liquid, a large amount of heat energy is required to remove the liquid and it takes a long period of time to effect disposal of the raw sewage.
In view of the drawbacks of the above conventional methods, the inventor proposed a disposing apparatus having a casing provided with stirring blades and heat-holding balls therein, in which the raw sewage is stirred by rotation of the stirring blades and heated by heat generated by the heat-holding balls, whereby the raw sewage is dried in a short period of time and the liquid is evaporated. This apparatus is disclosed in Japanese Patent Nos. 63-124150, 2-411577, and U.S. Pat. Nos. 4,999,930, 5,058,213, 5,152,074, 5,230,164, 5,257,466, and U.S. patent application Ser. No. 07/809,962 filed Dec. 18, 1991 abandoned, continuation application filed on Oct. 26, 1993, as Ser. No. 08/143,522 now U.S. Pat. No. 5,418,982 and Ser. No. 07/985,556 filed Dec. 3, 1992, now U.S. Pat. No. 5,261,126.
According to the above proposed disposal methods, the raw sewage is heated, evaporated in the casing and diffused into the ambient atmosphere. Before the liquid component is diffused, the components which cause bad smell are resolved by a catalyst so that the liquid water is diffused into the atmosphere as an odorless vapor. It was preferable to employ such a method in view of environmental hygiene and preservation, even if such method is employed in crowded buildings and/or by crowds of people.
It is very hygienic to evaporate and diffuse the raw sewage contained in the airtight tank and such operation can be carried out systematically, which results in not causing a burden to the operators. In the above-described raw sewage disposal apparatus as proposed by the inventor, raw sewage is contained in an airtight container (drying cauldron) and the lower portion of the airtight container is heated by a heater, etc. Thus evaporated vapor, etc. in the container are introduced into a dust collection box for removing dust from the evaporated vapor, etc., then introduced into a catalyst box, and then diffused in the atmosphere. The reason why the vapor evaporated in the airtight container is caused to contact the catalyst is that the bad smell component is changed into an odorless component, thereby preventing the bad smell from being diffused in the ambient atmosphere.
In this case, platinum is used as a catalyst to subject the bad smell component to oxidation-reduction. Accordingly, the catalyst must be maintained at a constant temperature. A catalyst heater is conventionally accommodated in the lower portion of the catalyst box. This catalyst heater contacts the evaporated vapor, which causes the catalyst heater to oxidize and causes trouble, for example, corrosion or breakage since ammonia, urea, etc., contained in the raw sewage contacts the catalyst heater. Accordingly, such catalyst heater cannot be used for a long period of time and is troublesome because of the maintenance and replacement thereof.
In order to heat the container containing the raw sewage, there is employed a method for supplying power to the container so as to energize a heater, so that the container is heated from the outside thereof, or another method for directly heating the container by combusting liquid fuel by way of a burner, etc. However, the method for heating the container by the heater is inferior in thermal efficiency since the entire heat is not transmitted to the container. On the other hand, in the method for heating the container by combusting liquid fuel, there is an advantage in that the structure of the container is simple but there are disadvantages in that a containing box surrounding the container and the burner is increased high in temperature, which can cause a fire and the heated container must be cooled, which makes the apparatus large. Furthermore, the method for heating the container by combusting liquid fuel can be employed in the outdoors, but it was dangerous in an indoor location since carbon dioxide is generated. In this prior art raw sewage disposal apparatus, stirring blades are rotated in the container so as to keep the heat uniform, which vibrates the container. If this vibration is transmitted to the heater, the heater may be broken, which takes time and labor for the maintenance thereof. Under the circumstances, there is desired a method for heating the container with high thermal efficiency and without generating carbon dioxide. There is also desired a method for heating the container without using materials which cannot stand much vibration of the heater, etc. under clean conditions at all times.